1. FIELD OF THE INVENTION
The invention relates to a mechanical latch having an hydraulic locking mechanism which permits selective and repeatable latching of a tubular string into a connector, such as a crossover assembly, and which permits locking and unlocking of the tubular string therein hydraulically and without requirement of rotation or longitudinal movement of the tubular string.
2. DESCRIPTION OF THE PRIOR ART
Subterranean oil and gas wells oftentimes are drilled through a plurality of producing zones. In order to isolate these zones for selective production purposes, plural tubing strings are inserted into the well during the completion or workover operations. For example, in a well having two production zones, a first or "long" string is inserted into the well. Near the lower end of the "long" string, a single bore packer mechanism may be provided for isolating the lower zone from the well bore thereabove. A crossover assembly is carried on the "long" string above the packer mechanism for receipt of a second or "short" string which may be utilized to, for example, pump corrosion inhibitor, other treating fluids, or kill fluids from the top of the well to the upper zone. In the event that it is desired to circulate the treatment fluid within the tubing strings above the packer and the lower production zone, a crossover assembly is utilized which contains a manipulatable valve or other assembly to permit selective opening and closing of a port therein for communication across the crossover assembly between the "long" and the " short" strings. Of course, the "short" string may be open-ended to permit production from the upper zone therethrough.
Heretofore, the "short" string has been landed on the cross-over assembly, stung therein and locked by mechanical means, such as by use of a J-slot assembly or a snap-type collet hatch. To lock or unlock the "short" string within a J-slot locking mechanism typically required righthand rotation of the "short" string to come out of the J-slot mechanism into either the locked or unlocked position therein. In deviated holes, such mechanical rotation is oftentimes extremely difficult and does not provide an accurate indication of the locked-unlocked position with respect to a given number of tubular rotations recorded at the top of the well of the "short" string. In addition, such mechanical means typically do not permit selective and repeatable latching into the crossover assembly prior to the locking mode, in order to permit initial setting and location of the "short" string and thus permit retrieval of the tubing for purposes of accurately spacing out the "short" string at the wellhead. Failure to permit selective and repeatable latching prior to locking heretofore has meant that the "short" string would have to be stung into the crossover assembly prior to accurate spacing. This, in turn, has resulted in considerable tension being applied at and upon the latch due to expansion and contraction of the "short" tubing string as the result of injection or transmission of fluid therein. Accordingly, considerable set down weight has been required for application to the "short" string while it is locked into the crossover assembly to overcome the mechanical forces caused by thermotic variation.
The reliability of the lock of the "short" string into the crossover assembly in such an apparatus has been directly dependent upon the strength of the mechanical locking mechanism which, in turn, has been affected by temperature and pressure variances within the interior of the "short" string.
Of course, the deeper the well bore, the more tubing set down weight which has been required to be applied to the locking mechanism. Moreover, since tubular rotation may be required to latch and/or lock and unlock the "short" string within the crossover assembly, such rotational movement obviously is considerably more difficult to accomplish in dual completion wells utilizing a plurality of tubular strings.
The problems associated with the above-described prior art locking mechanisms are solved by utilization of the present invention which permits latching of a "short" string, or any given tubular string, into a conduit therefor by longitudinal manipulation of the "short" tubular string. Thereafter, the "short" string may be repeatably latched and unlatched until such time as it is desired to lock the "short" string into the conduit. The locking procedure does not require tubular manipulation, but is accomplished by hydraulic means. Unlocking of the apparatus also is accomplished by hydraulic means.